An optical cross-connect assembly is an assembly that is used to interconnect optical fiber communications modules with one another. An optical fiber communications module may be an optical transceiver module having both transmit and receive optical channels, an optical transmitter module having only transmit optical channels, or an optical receiver module having only receive optical channels. An optical cross-connect assembly may be used to interconnect many such optical communications modules with many other such optical communications modules.
Optical cross-connect assemblies take on a variety of forms depending on the applications in which they are used. In smaller-scale applications, printed circuit boards (PCBs) having electrical-to-optical and optical-to-electrical conversion elements coupled to fiber assemblies and optical waveguides are used as optical cross-connects to optically interface one or more optical communications modules with one or more other optical communications modules. In larger-scale applications, many optical communications modules are contained in boxes that are held in slots of large racks. In these types of applications, it is not feasible to use PCB solutions to optically interface the boxes with one another. The optical cross-connect assemblies that are used in these types of applications are typically optical fiber cables having LC or MTP connectors on each end that are manually connected to ports of the boxes.
In some larger-scale applications, it is necessary to optically interconnect all of the boxes in a rack or multiple racks with all of the other boxes in the same racks. Each box typically contains one or more processor elements (PEs), such as, for example, central processing units (CPUs), application specific integrated circuits (ASICs), or application-specific standard products (ASSPs) that enable an interconnect, switching, routing, or other such function. By interconnecting all of the boxes with all of the other boxes, all of the PEs of all of the boxes can be configured to operate as a single large-scale system. In computing applications, optical cross-connect assemblies are used to enable the construction of supercomputers. In routing and switching applications, optical cross-connect assemblies are used to make large numbers of interconnections for the purposes of switching or routing large amounts of data between large numbers of sources and destinations. In redundant arrays of inexpensive disk (RAID) systems, often times the boxes in a rack or in multiple racks are interconnected to allow data that is stored in the memory device of each box to be duplicated, or striped, in the memory devices of all of the other boxes. In some larger-scale applications, all of the boxes of one or more racks are interconnected with all of the boxes of one or more other racks.
In all of these types of larger-scale applications, it can be difficult to connect each box to all of the other boxes using optical fiber cables and connectors. For example, assuming that a rack contains 128 boxes that must be interconnected with one another, each box would need to be connected to 128 transmit optical fiber cables and 128 receive optical fiber cables. This scenario corresponds to a radix of 128. Providing enough ports on each box to accommodate these interconnections can be difficult. Also, it is difficult to drive signals, especially at high speeds (e.g., gigahertz speeds), across electrical cables that have rack-sized lengths. Electrical cables are sometimes used within a rack to make interconnections between boxes, but it is impractical to use them over long distances due to the fact that they are bulky in size and very lossy, i.e., they waste a lot of electrical power at high speed and over long lengths. Making a PCB with optical waveguides on it that is large enough to accommodate this many interconnections is not practical because the PCB would have to be as large as the rack or large enough to span across multiple racks.
Accordingly, a need exists for an optical cross-connect assembly that is suitable for use in small-scale and large-scale applications, and particularly well-suited for use in high-radix applications where a large number of interconnections need to be made.